Tevatron ColliderStatus and Prospects
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Ron Moore
Fermilab – AD / Tevatron Dept.
APS DPF 2009 – Wayne State University
Contents
• Overview
• Luminosity Evolution
• Operational Considerations
• Prospects and Projections
• References to other FNAL talks in the Accelerator sessions…– Vladimir Nagaslaev – Antiproton Production at Fermilab (Accelerator 3)
– Sasha Shemyakin – Antiproton Accumulation and Cooling at the Fermilab Recycler Ring (Accelerator 1)
– Phil Adamson – Fermilab Main Injector (Accelerator 3)
– Mary Convery – Optimization of Integrated Luminosity of the Fermilab Tevatron Collider (Accelerator 1)
APS DPF 2009 – Wayne State University
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Looking Down on the Fermilab Accelerator Complex
1 km
Main Injector
& Recycler
Tevatron
Pbar Debuncher & Accumulator
D0
CDF
APS DPF 2009 – Wayne State University
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Tevatron Overview
• Synchrotron providing proton-pbar collisions @ 980 GeV beam energy
– Injection energy is 150 GeV
• Tevatron radius = 1 km revolution time ~ 21 s
• Virtually all of the Tevatron magnets are superconducting
– Cooled by liquid helium, operate at 4 K fun fact: ≈350 MJ stored energy!
• 36 bunches of proton and pbars circulate in single beampipe
– 3 trains of 12 bunches with 396 ns separation
– Electrostatic separators keep beams apart on helical orbits
• 8 Cu RF cavities to keep beam in bucket, provide acceleration
– 1113 RF buckets (53.1 MHz 18.8 ns bucket length)
• 2 low (small beam size) intersection points (CDF and D0)
APS DPF 2009 – Wayne State University
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Tevatron
Tev dipole
The Big Picture
APS DPF 2009 – Wayne State University
Record month Dec 2008 ≈ 250 pb-1
Record weekly delivered luminosity = 73.1 pb-1
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Record month Dec 2008 ≈ 250 pb-1
Record weekly delivered luminosity = 73.1 pb-1
The Logarithmic Big Picture
APS DPF 2009 – Wayne State University
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Tevatron Peak Luminosity
APS DPF 2009 – Wayne State University
each point is one store > 300 µb-1/s now routine
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Beam Intensities
APS DPF 2009 – Wayne State University
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10000 109 278 109 / bunch 3000 109 83 109 / bunch
Destroyed Collimators in Tevatron (2003)
APS DPF 2009 – Wayne State University
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Protons
prompted a faster quench protection system
tungsten
Stored beam energy
1013 protons @ 1 TeV ≈ 1.6 MJ
Damage done in ~10 ms
1.5 m long stainless steel
APS DPF 2009 – Wayne State University
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Increasing Tevatron Luminosity
• Many gradual improvements
• Higher antiproton stacking rate → more antiprotons faster
• Recycler + Electron Cooling → more pbars with smaller emittances
• Smaller β* at CDF and D0 → smaller beam size (now down to ≈30μm)
• Improved beam lifetimes in Tevatron
– More separation between protons and antiprotons
• Better instrumentation, monitoring
• Better reliability, reproducibility
)()(2
**
z
ap
ap HNfN
L
• N = bunch intensities, f = collision frequency
• ε = transverse emittance (size), σz = bunch length
• H = “hour glass” factor (~0.6 for finite bunch length)
APS DPF 2009 – Wayne State University
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Magnet Motion / Orbit Stabilization
V. Ranjbar
Orbit stabilization ON
E11 vert BPM [mm]
F17 horz BPM [mm]
D0 proton halo [Hz]
Proton vert tune
C4Q4 roll [μrad]
C4Q4 pitch [μrad]
Proton intensity [E9]
Store 4402
New BPM electronics help us see this motion!
APS DPF 2009 – Wayne State University
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Strategy: Be Efficient, Be Consistent
• Big upgrades are done ⇒ Make the most of what we’ve got!
• Make HEP shot-setup more efficient– “One-shots” for Tevatron injection when needed – allows more pbar stacking cycles– Automation of tune, coupling, chromaticity measurements/settings– Working on faster proton injection → 2 bunches per shot instead of 1
• Increased/improved automation– Tune, coupling, chromaticity measurements/settings during shot-setup
– Orbit smooths during/between HEP stores• Reduce orbit drifts store-to-store, keeps optics consistent; sneak beam losses through IPs
– Faster scraping/halo removal– Beam-beam tune shift control
• Automated proton tune settings to account for varying pbar intensities shot-to-shot
• Monitor decrease in beam-beam tune shift during store, alert operators to nudge up
• Shorter HEP stores– Higher average pbar stacking rate → shorter stores for ≈ same initial lumi– More stores with higher average luminosity over store duration
Stack, Stash, Store - Repeat
APS DPF 2009 – Wayne State University
our record week
Accumulator [1010]
Recycler [1010]
Tevatron Luminosity
[μb-1 / s]
Stack pbars in Accumulator shoot to Recycler stash
HEP stores
Shoot pbars from Recycler to Tev for HEP
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More Integrated Luminosity per Store
APS DPF 2009 – Wayne State University
- More integrated luminosity per store hour
- Running shorter stores ⇒ more stores / week
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Beam-Beam Effects
• Recall both beams circulate within a single beam pipe!– EM fields from one beam disrupts the other when passing
near/through it
• Head-on and long-range collisions (parasitic or “near-miss”) – Would like > 5σ separation between beams prior to collisions
• Not always possible
– Affects all aspects of operation – injection, acceleration, squeeze,…
• Highest antiproton intensities are problematic– Antiprotons 3-4x smaller transversely than protons
– High proton losses occasionally quench the Tevatron in squeeze
– Early in HEP proton lifetime can dominate lumi lifetime
– Occasionally back off beam intensities to sort out issues
APS DPF 2009 – Wayne State University
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APS DPF 2009 – Wayne State University
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Head-On Beam-Beam Effects
• Head-on collisions: each beam acts as (non-linear) focusing lens
– Tune gets shifted up proportional to (N / beam size)
– Tune footprint also spreads out – unavoidably crossing resonances
– NP ≈ 250 (10)9 εP≈ 18π mm-mrad → ξA ≈ 0.020 (pbar shift from protons)
– NA ≈ 70 (10)9 εA≈ 5π mm-mrad → ξP ≈ 0.020 (proton shift from pbars)
– Beam-beam tune shift on protons ≈ pbars!
Nr
2
3 0• N = bunch intensity
• ε = transverse emittance
• r0 = classical radius of proton
Head-on beam-beam
tune shift parameter
2 collision
points
APS DPF 2009 – Wayne State UniversityR. Moore - FNAL 18
0 1 2 3
Beam-beam force Proton density Antiproton density
r/
Schematic of Beam-Beam Force on Proton Bunch
Round, gaussian bunchesproton pbar
x
y
A significant fraction of the proton bunches feel the strongest, non-linear beam-beam force from the smaller pbars
Arb
itrar
y un
its
APS DPF 2009 – Wayne State University
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Beam-Beam Tune Shift Distributions
M. Syphers
Equal bunch sizes
Protonsbroad tune shift
Pbarspeaked
tune shiftσP = 2 σA
Δν / ξ
dN /
dR
for
a b
unch
4/7 = 7th order
7/12 = 12th order
3/5 = 5th order
Beam-Beam Tune Spread
Tune spread caused by pbars causes
proton tunes to span strong resonances
→ higher beam loss and/or poorer lifetime
APS DPF 2009 – Wayne State University
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This is just an “artist’s rendering” of the
beam-beam induced tune spread…
APS DPF 2009 – Wayne State University
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Mitigating Beam-Beam Effects
• Since ~Feb 08 deliberately “blowing up” antiprotons by ≈25% at flattop
– Noise source on directional stripline
– Reduce the emittance mismatch → proton tune spread
– Helps beam losses in squeeze and in collisions
– Would like to optimize the scheme, account for bunch-by-bunch differences
• Also testing scraping higher intensity protons @ 8 GeV in Main Injector
– Bump beam into collimators, remove tails that would be lost in Tevatron
APS DPF 2009 – Wayne State University
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Proton Loss in Squeeze vs Pbar Intensity
Long-range beam-beam effects: higher pbar intensity → higher proton loss
APS DPF 2009 – Wayne State University
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Store 6908 – Comparison to Model without Beam-Beam Effects
Initial Lumi = 320 μb-1/s
only ~5% luminosity loss from beam-beam effects!
Protons suffer from beam-beam effects
Luminosity Integral Proton IntensityModelData
A. Valishev
APS DPF 2009 – Wayne State University
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Beam Lifetimes during HEP• Pbar lifetime dominated by luminosity – good• Most protons lost in non-luminous processes – but better with larger pbar emittances
Luminosity[μb-1/s]
Pbar Lifetime
/ ExpectedLifetime from
Luminosity
Store 6203
Proton Lifetime
/ ExpectedLifetime from
Luminosity
1
0.75
0.5
0.25
0
300
225
150
75
0
Reliability
APS DPF 2009 – Wayne State University
Year StoresNormal
Terminations%Normal
Terminations
Avg Store Hrs/Week (outside
of planned shutdowns)
2003 186 55 30% -
2004 166 110 66% 100
2005 243 170 69% 110
2006 171 107 63% 100
2007 220 177 80% 110
FY2008 304 262 86% 106
FY2009 275 244 88% 110
Improving
Reliability
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Prospects
• More pbars (faster) still most straightforward way to higher luminosity
• Believe Tevatron can deliver peak luminosity > 400 µb-1/s– As a stunt, since integrated lumi would fall off @ current stacking rates
• Squeeze losses still a concern, so still blow up pbars @ flat-top
– Identified aperture restriction on B-side of CDF (displaced beam pipe)
– During Oct 08 shutdown, found pipe misaligned as expected– Moved pipe successfully to open up aperture (though not quite
centered)
• All machines continue working on operational robustness, efficiency
• Quote from my boss (Roger Dixon) in Fermilab Today: – “…the Accelerator Division has no shortage of innovative people who get an
adrenalin rush from making unexpected improvements that could make our projections look silly.”
APS DPF 2009 – Wayne State University
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Luminosity Projections
• > 2.5 fb-1 / year is reasonable goal– No shutdowns, still need to be lucky
• 12 week shutdown began June 15– Install rest of new Booster correctors, poke holes in MI for NOνA– Find and fix known leaks in 8 of 24 Tevatron cryogenic houses
APS DPF 2009 – Wayne State University
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• 200 pb-1 / month has become routine
Luminosity Projection
APS DPF 2009 – Wayne State University
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currently 6.8 fb-1 delivered
real data for FY02-FY08
9.3 fb-1
7.8 fb-1
Inte
gra
ted
lu
min
osi
ty (
fb-1)
---------
FY04 FY05 FY06 FY07 FY08 FY09 FY10 FY11
~12 fb-1
have achieved design parameter goals of Run II
on track for ~12 fb-1 through FY11 even with no further
improvements
Summary
• Tevatron and whole accelerator complex running great– delivered ≈ 3.5 fb-1 over last running period (Oct 07-Jun 09)
– now approaching 7 fb-1 total in Run 2
• Peak lumi > 300 µb-1/s and integrated > 200 pb-1/month routine
• Ongoing efforts to improve operational efficiencies and get more pbars/week and HEP stores with greater lumi/hr
• Could deliver > 9 fb-1 by end FY10 and nearly 12 fb-1 by end FY11– Let’s go all the way through FY11!
• Looking forward to physics results from both CDF and D0
APS DPF 2009 – Wayne State University
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Tevatron HEP Store Lengths
APS DPF 2009 – Wayne State University
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Collider Operational Model
APS DPF 2009 – Wayne State University
C. Gattuso
curr
ent r
egim
edepends on pbar stacking
rate and lumi lifetime
75 pb-1 ≈ consistent with our best week
Integrated luminosity optimized with 15-20 hr stores to build up stashes of 350-400 1010 pbars
at current stacking rates
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Making HEP Shot-Setup Faster
APS DPF 2009 – Wayne State University
- faster manipulations in Recycler- ongoing tweaking and automation in
Tevatron-recently started 2-bunch proton
injections- faster halo removal
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